With increasingly growing requirements of mobile broadband data services, for a broadband radio access network, a wireless communication system with a large number of spectrum resources of adjacent radio frequencies needs to be deployed. In addition, after the wireless communication system is deployed, with the increasing requirement of a higher data rate, the requirement of the performance of the broadband radio access network is also improved. For example, a broadband video requires a large amount of bandwidth, but it is increasingly difficult to provide such bandwidth using limited radio frequency spectrum resources generally allocated to the wireless communication system. In addition, more and more users are transferring to the wireless communication system to obtain its communication services. This may increase the load of the wireless communication system and may further reduce the bandwidth available for each user or the available bandwidth of the whole wireless communication system. Therefore, it is necessary to improve the performance of the wireless communication system by more efficiently using the available radio frequency spectrum or available bandwidth of the device, network or system.
In the wireless communication system, each cell under a base station generally has only one carrier and a terminal is capable of receiving and sending data only in one cell (on one carrier) at a time. The carrier may be a component carrier (component carrier, CC for short), may occupy a part of the bandwidth of the wireless communication system, and may also be a minimum allocatable unit, for example, multiple time domains on multiple schedulable subcarriers in a subframe. In a Long Term Evolution system (LTE for short), the maximum bandwidth of a carrier is 20 MHz. In a Long Term Evolution-Advanced system (LTE-A for short), the peak rate ratio of the wireless communication system is greatly improved compared with that in the LTE, and requires that the downlink peak rate reaches 1 Gbps and the uplink peak rate reaches 500 Mbps. Therefore, the transmission bandwidth of 20 MHz cannot satisfy this requirement. To provide a higher transmission rate, the LTE-A adopts a carrier aggregation technology. The carrier aggregation technology refers to that a terminal is capable of combining multiple carriers and transmitting data on the carriers at the same time, thereby improving the data transmission rate. The bandwidth of each carrier does not exceed 20 MHz for ensuring that in the LTE-A, the terminal is capable of working under each aggregated carrier.
At present, how to properly schedule and allocate, to the terminal, carrier resources that can be aggregated is a main problem to be solved in the industry.